Formation and evolution of a carbon-rich star with 2.8 Msun.

The author builds a theory for stellar structure and evolution taking into account turbulent pressure based on the mixing-length theory of convection, and presents a criterion for the occurrence of dynamic instability in the convective envelope of a RGB or an AGB star. According to this he performs calculation for evolution of a star with 2.8 M_sun from the main sequence to the RGB stage and the AGB stage. The results show that the turbulent pressure in the regions close to the surfaces of the RGB star and the AGB star can reach a value of 30% of the total pressure, and that the effect of turbulent pressure can cause a dynamic instability in the regions close to the surfaces of the RGB star and the AGB star, which affect the mass escape outwards. And this may be the mechanism for driving the strong stellar winds of RGB stars and AGB stars with very low surface temperature and faint radiation pressure.